Dielectric medium



March 9, 1937. A. E. MAIBAUER 2,073,245

DIELECTRIC MEDIUM Filed Sept. 8, 1933 INVENTOR A'Z5e1'ZEMaz'6azze1:

112}? ATTORNEY Patented Mar. 9, 1937 PATENT orric DIELECTRIC MEDIUM Albert E. Maihauer, Bloomfield, N. 5., assignor to Halowax Corporation, New York, N. 1., a corporation oi? Delaware pp ati n September 8, 1933. Serial No. teams 4 Claims.

This invention relates to an impregnating, insulating and dielectric material for use in electrical apparatus, for instance condensers, trans formers, oil switches, etc.

5 Apparatus of this type has usually been made with petroleum oils filling the space between the electrical conducting parts and in some cases also between such 'parts and the container, and impregnating the body in the case of condensers.

Such petroleum oils are by no means ideal liquids for this use because they are inflammable and have a comparatively low dielectric constant.

The hereinafter disclosed filling and impregnating materials have a very low power factor thereby absorbing very little power and they also have high insulating resistance so that there is very little leakage current passing between the conducting elements. Certain of these materials also have a low viscosity and high heat conductivity, and for this reason they are very mobile within the jacket or container and very thor-- oughly and quickly dissipate the heat generated in the apparatus, by quickly absorbing the heat from the body of the apparatus and then moving to the jacket where the heat is given up. The

materials have a very low volatility and therefore very little of the materials are lost when they are heated for instance in an impregnation chamher to impregnate the condenser body; and after the condenser or other container is sealed, they generate substantially no pressure within the container, thereby overcoming all dangers of bursting the container or injuring the condenser body or other apparatus even though light weight parts are used. A condenser impregnated with these materials has approximately per cent or more greater capacitance for the same active foil or plate electrode area than has a condenser impregnated with the usual petroleum oils. In addition the materials are very stable and resistant to oxidation. Other objects and features of the invention will more fully appear from the following claims taken in conjunction with the accompanying specification and drawing which, however, must be understood as illustrating merely one form of the invention and in no way limiting it to the specific embodiment shown and described.

The single figure of the drawing is a diagrammatic sectional view of one form of condenser in conjunction with which the hereinafter described impregnating and filling materials may be used.

The invention will be described in connection with a so-called oil condenser as illustrating the 55 use of these materials not only as cooling and insulating media but also as impregnants and di electrics. For some uses, for instance in oil switches, the dielectric effect is not so important as non-inflammability whereas in transformers the dielectric, cooling and principally the noninflammability characteristics are important.

The so-called oil condensers are principally used on alternating current circuits where dielectric losses are much greater than in direct current circuits. the hereinafter described materials in the liquid oily condition are generally better than the solid wax impregnated condensers because there is less likelihood of their breaking down, they can oper ate at larger loads, there are less electrical losses, and a reduced corona effect. The oily material which is used in the condensers should quickly absorb and dissipate any heat which is generated and, in particular, should thoroughly protect the weakest parts of the condenser that is the points at which a breakdown is most likely to occur, by absorbing the heat caused by leakage of the electric current across the weak place and then dissipating this heat. The oily material should at all times be ready to seep into and insulate any weak place and should not deteriorate due to the heat or due to the comparatively excessive passage of current between the electrode elements oi the condenser at the weak points as compared to the main area of the condenser. The oily materials should have high electrical resistance and should also have excellent dielectric properties so that the oily liquids both prevent the passage of electricity by conductivity from one of the electrode elements to another, and provide a condensing media which has an exceedingly high capacitance for the electrode area. The physical characteristics of the oily materials not only enable them to move freely within the con denser jacket so as to dissipate heat but also enable them to thoroughly impregnate the entire body of the condenser, which these liquid compounds are at all times ready to do because of their physical characteristics. They are not af= iected either by the normal operating voltage which is on the condenser or by the electricity which may pass between the condenser electrodes. The mate-rials not only have a low volatility at high temperatures but they remain liquid at low tempe atures, that is at temperatures suhstantially below 0 C., and the viscosity is not appreciably affected by changes in temperature. The materials which have these desirable characteristics to a marked degree, are liquid organic esters of phenols which phenols have boiling Condensers impregnated with boiling phenols.

point above 210 0., known in the art as high These high boiling phenols comprise for instance xylenol," trimethyl phenol, triethyl phenol, and methyl-ethyl phenol; mixtures of these high boiling phenols with low boiling phenols, for instance, a mixture of 1 molecular weight. of phenol with two molecular weights of ortho phenyl phenol, made into mixed esters, particularly those liquid organic esters of phosphoric acid, may be used. I have found particularly useful, esters containing polyphenol groups for instance those made from hydroxy diphenyl or mixtures of these esters with mono phenyl esters. For example; such polyphenyl esters can be used after merely distilling and are found of.

suflicient resistivity for most uses, therefore do not require those special and expensive methods of purification, needed for pure esters of the lower boiling phenols.

Other materials are liquid esters of phosphoric acid wherein the acid hvdrogens are substituted by phenols having for instance suflicient .alkyl group substituents to raise the boiling point above 210 C. as for instance, two methyl groups or 1 butyl group, '1 phenyl group or other aryl groups, etc. 'Such mixtures of high and low boiling phenols may be used as do not boil below 210 C. at 760. m. m. pressure when the thermometer is placed in'the mass of the mixture. Thus the reaction products of substituted arc-'- matic materials of high boiling point, for instance chlorophenol and phosphorus oxychloride, give both chlorine and oxygen bearing organic phosphorus compounds of high dielectric value. The esters of phosphoric acid and high boiling phenols such as xylenol may. be used and one or more of the xylenol radicals may be substituted by phenols as, for instance, in xyletic phenyl phosphate. The polphenyl phosphates include the esters of phosphoric acid and polyring phenols for instance xenyl phosphate or those esters having a mono phates for instance phenyl-di-orthodiphenyl phosphate. three replaceable hydrogen atoms from which mixed aryl esters may be prepared for instance a phosphate having one or more hydrogen atoms reacted with xylenol, and one or more replaced with other radicals such as cresyl, etc., giving for example cresyl xyletic xenyl phosphate. Mixtures of these preferred esters may also be used with other esters for instance a mixture of triorthoand para-diphenyl and triphenyl phosphates with liquid discresyl phthalate made from a mixture of ortho", meta and para cresol.- The compounds which are preferably used remain liquid below C. and are substantially non-volatile at 90.

In making a'condenser using these materials, the electrode elements 2, and the insulating elements 6, are assembled in their proper position to form a condenser body 6, which is held in assembled relation by clamps 8. Lead wires it are Normal phosphoric acid contains connected to the conducting electrode elements 2, and then brought out of the condenser body 6. The condenser body is then placed within a container l2,'and held in place by spacers l4. The lead wires ID are connected to contacts 16, which are insulated from and fastened into the top 18 of the condenser. The top of the condenser is provided with openings 20, which are to be closed by solder or similar material 22, after the condenser is, filled with the impregnating material.

After the condenser body is within the container and the top is sealed in place butwith the openings 20, unsealed, the entire unit is placed within the chamber of an impregnating apparatus where the unit is heated and subjected to vacuum. The heat and vacuum take the air and moisture from the condenser which, preferably without breaking the vacuum, is then impregnated with one, or a mixture of, the previously mentioned insulating materials. The insulating materials not only impregnate the body of the condenser but fill the container. When the condenser body is thoroughly impregnated, the unit is removed from the impregnating chamber and, preferably while still hot, the openings 20, are sealed with the sealing material 22.

The resulting condenser unit is one which will last longer than a unit impregnated with a solid dielectric and it has a much higher capacity for a corresponding electrode area, than a condenser impregnated with a petroleum oil, these advantages being derived by the impregnation of the condenser body and filling the container with the previously mentioned impregnating and insulating materials having the aforesaid characteristics.

v From the foregoing description it is obvious that many diflerent impregnating materials and combinations thereof may be used and that various other modifications of the invention may be made and, although a particularform of the invention has been described, it is recognized that these modifications are possible. It is therefore desired that the invention be construed as broadly as the claims, taken in conjunction with the prior art, may allow.

I claim:

1. A liquid insulator and dielectric for use in electrical devices comprising phenyl-di-orthodiphenyl phosphate.

2. A liquid insulator and dielectric for use in electrical devices comprising principally at least 

